1. Field of the Invention
The present invention relates to a silver halide photographic emulsion, and a silver halide photographic light-sensitive material containing the photographic emulsion, and more particularly, to a silver halide photographic emulsion having a high sensitivity, a high contrast, an improved pressure-resistant characteristic, and an improved latent image storability, and a silver halide light-sensitive material containing such photographic emulsion.
2. Description of the Related Art
Methods of producing and techniques of using tabular silver halide grains are disclosed in, for example, U.S. Pat. Nos. 4,434,226, 4,439,520, 4,414,310, 4,433,048, 4,414,306 and 4,459,353, and JP-A-59-99433 (JP-A means Published Unexamined Japanese Patent Application), and advantages including the enhancement of spectral sensitization, the improvement of sensitivity/graininess and the improvement of sharpness are discussed in these documents.
Further, JP-A-63-11928, JP-A-63-151618 and EP-514,4742A disclose techniques in which tabular grains are monodispersed in terms of size distribution, and the ratio of tabular grains present is increased.
However, there are a number of problems with the tabular silver halide grains which should be solved in introducing into a photographic light-sensitive material, especially in durability such as pressure-resistant characteristics and latent image storability.
In the meantime, JP-A-3-168734 and JP-A-3-211543 disclose techniques for improving the color reproducibility and reciprocity failure property by using a silver halide photographic emulsion containing twinned crystal grains having an aspect ratio of 5 or more in an amount of 50% or more of a total projected area of all grains, wherein a (420) X-ray diffraction signal obtained using K.sub..alpha. line of Cu has only one peak, and the diffraction ray width at a maximum peak height.times.0.13 is less than 1.5 degree or more in terms of angle of diffraction.
Further, JP-A-3-241336 discloses techniques for improving the sensitivity and graininess by using a silver halide photographic emulsion containing twinned crystal grains having an aspect ratio of 5 or more in an amount of 50% or more of a total projected area of all grains, wherein a signal is present over 1.5 degree or more of a diffraction angle at a maximum peak height.times.0.13 of a (420) X-ray diffraction signal obtained using K.sub..alpha. line of Cu.
However, in these silver halide emulsions, the aspect ratio of the tabular silver halide grains are relatively low, and the monodispersity of the grain size and the ratio of the tabular grains present are not high enough, so that a sufficient improvement effect of the photographic properties, which is an advantage of tabular grains, cannot be obtained. Therefore, there has been a demand for a further improvement of sensitivity and gradation, as well as properties of durability such as pressure-resistant characteristics and latent image storability.